This invention relates to the visual presentation of information derived from a stereoscopic (3D) image system.
In normal circumstances this information would be viewed using any one of the well known techniques for stereoscopic viewing. Many of these are particularly suited for use with video type displays monitors.
Alternative displays known as 2xc2xdD representations (referred to as 3D by the computer graphics fraternity) in fact contain only psychological cues to depth such as linear perspective, interposition, shading and shadowing, rather than the powerful physiological depth cue known as binocular parallax or stereoscopy, i.e. a true 3D image.
Using these 2xc2xdD representations it is possible to manipulate the image information in a number of ways which provide alternative views of the same object. Examples are image rotation and layer removal. These display techniques have proved particularly beneficial for the viewing of images derived from computed tomography (CT) and magnetic resonance (MR) scanners which are now widely used by the medical profession. Both of these types of scanners produce information in a slice by slice format and a great deal of software has already been developed to convert this multiple slice information into the 2xc2xdD representation.
Stereoscopic pairs of images can be obtained in a variety of ways. They are effectively left and right two dimensional perspectives of a scene or object which are analogous to the two perspectives seen by the eyes of a human observer. The images may be displayed as photographs, radiographs, video pictures and so on.
The fundamental element of a stereoscopic pair of images is that in general the image point of an object in say the left perspective will have a corresponding or conjugate point in the right perspective. The parallax which exists between the same image point in each perspective is a measure of the Z-coordinate, i.e. depth, of that point. Consequently, there will be a number of resolvable depth planes or slices in a stereoscopic display which are separated by an amount which is related to the minimum detectable parallax in the display. For example, in a stereoscopic video display the minimum resolvable parallax will be defined by the pixel resolution in the system, which in turn defines the density of depth planes in the display. This minimum detectable parallax will depend upon the parameters of a particular display and in, for example, a situation where the images are optical images to be viewed by an observer, will depended upon the minimum resolution of the eye. Where the images are to be presented on a say a video monitor then the minimum detectable parallax will be fixed by the minimum pixel resolution in the overall system which may, for example, be the resolution of the monitor.
It is therefore an object of this invention to identify points at each particular depth plane or slice to build up the required 2xc2xdD image.
According to the invention there is provided a method of creating a 2xc2xdD solid model picture for viewing, in which a stereoscopic image is identified as a series of depth slices and the resulting slice data built up to a 2xc2xdD model using software which transforms the slice data.
Also according to the invention there is provided a method of creating a 2xc2xdD solid model picture for viewing, comprising:
a) comparing a stereoscopic pair at one relative lateral position and identifying points of coincidence to represent a slice through the picture at a depth corresponding to that particular relative lateral position,
b) moving the pair laterally relative to one another by an amount equal to the minimum detectable parallax in the stereoscopic pair and repeating step a,
c) repeating step b as often as required to identify points of coincidence at all parallax depths or slices of the stereoscopic picture, and
d) building up the 2xc2xdD solid model image by using the slice data so obtained.
Thus, having obtained the required depth information in a form equivalent to a number of slices, one can then utilize software, and in particular there is already available suitable software, which can then convert this slice data into solid 2xc2xdD models. One can therefore build 2xc2xdD models from these original stereoscopic images.
According to the invention therefore it has been appreciated that a stereoscopic image can be considered to be a series of slices and that if the slice data can be identified, then software, such as that which already exists, can be used to build the 2xc2xdD model.